Researchers, including a Purdue University professor of earth and atmospheric sciences, discovered that a critical surface temperature feedback is twice as strong as what had been projected by earlier studies.
The high-resolution climate model used by the team was better able to reproduce the complex topography of the western United States and capture details of the effect of snow cover on the climate system, as well as the historical record of runoff.
According to Noah Diffenbaugh, senior author of the paper and an associate professor of earth and atmospheric sciences at Purdue University, the influence of melting snow on regional climate is far greater than that of increased greenhouse gases alone.
"The heat trapping from elevated greenhouse gases triggers the warming, but the additional warming caused by the loss of snow is what really creates the big changes in surface runoff," said Diffenbaugh.
"The big surprise here is how much the complex topography plays a role, essentially doubling the threat to water resources in the West," he added.
The melting snow contributes to a feedback loop that accelerates warming, according to Sara A. Rauscher, lead author of the study.
The amount and timing of the runoff from snowmelt is critical to the success of water management in the western United States.
Water resources for the area are reliant on snow acting as a natural reservoir during the cold season that melts and releases water in the warm season.
Changes in this timing could create problems in meeting the increasing demand for water in large urban and agricultural areas during the hottest summer months, according to Diffenbaugh.
"If the snow melts earlier or if it comes as rainfall instead, it would create a strain on infrastructure," he said.
"The current system relies on water being stored in the mountains as snow. So earlier runoff could mean too much water for the reservoirs early in the year and not enough available later in the year," he added.
According to Gregg M. Garfin, deputy director for science translation and outreach at the Institute for the Study of Planet Earth at the University of Arizona, dry summers could lead to more severe wildfires and changes in the ecosystems of the West.
"Early snowmelt and warmer soil temperatures could result in further massive forest mortality and an increased risk of wildfire activity," said Garfin.
"If these projections become reality, then the ecosystems of the northern and central Rockies will undergo dramatic changes with ramifications for wildlife habitat, fire potential, soil erosion and tourism," he added.